Many people experience difficulty in rising from a seated position or seating themselves from a standing position. This difficulty may arise from a variety of causes such as arthritis, other chronic illnesses, injuries or obesity.
The prior art demonstrates many attempts to assist such people with seating assist devices. In particular, pneumatically inflated devices are described in U.S. Pat. Nos. 4,629,162 (Porche, Dec. 16, 1982) and 5,361,433 (Vanzant, Nov. 8, 1994) and PCT Application PCT/GB96/01001 (Jeans). Each of these prior art devices includes an inflatable cushion and a detached blower unit, and each requires an external power source. Although these devices are portable, the separation of the cushion and the blower is an inconvenience. Further, these devices may only be used where an external power source is available, such as ordinary household electrical outlets.
Other prior art devices are more portable and do not require external power. The device described in European Patent Application No. 95200105.5 (Haan) uses a support member which is urged by torsion leaf springs to a raised position above a base member. The support member is hinged to the base member using an intermediate support member which allows the support member to remain relatively horizontal through its range of motion. Other hinged devices such as that described in U.S. Pat. No. 5,116,100 (Iversen, May 26, 1992) cause their users to be propelled forward rather than lifted upwards which is a significant disadvantage. The Haan device suffers from the drawback of all spring-activated devices in that the level of assist is governed by the strength of the spring. If too strong a spring is used, the device becomes difficult to use, as the speed of assist is uncontrollable. The device also becomes very difficult to close. If the spring is not strong enough, there is insufficient force to provide any real assistance to the user.
The prior art devices also suffer from a lack of stability or steadiness. Spring-activated devices will bob up and down as the user shifts his or her weight. The Vanzant device attempts to provide stabilization by inflating rear and side wall cavities first before inflating the centre cavity.
There is therefore a need in the art for a seating assist device which is conveniently portable, self-contained and which may be used on any seating surface. It may be further advantageous if such a device were to be stable and allow convenient operation which is controllable and adjustable by the user.